Traditionally, inorganic materials have dominated the semiconductor industry. For example, silicon and gallium arsenide have been used as semiconductor materials, silicon dioxide has been used as an insulator material, and metals such as aluminum and copper have been used as electrode materials. In recent years, however, there has been an increasing research effort aimed at using organic materials rather than the traditional inorganic materials in semiconductor devices. Among other benefits, the use of organic materials may enable lower cost manufacturing of electronic devices, may enable large area applications, and may enable the use of flexible substrates as supports for electronic circuitry in display backplanes, integrated circuits RFID tags, and sensors.
A variety of organic semiconductor materials have been considered, the most common being fused aromatic ring compounds as exemplified by acenes. At least some of these organic semiconductor materials have performance characteristics such as charge-carrier mobility, on/off current ratios, and sub-threshold voltages that are comparable or superior to those of amorphous silicon-based devices. Typically, these materials have been vapor deposited since they are not very soluble in most organic solvents. When organic semiconductors have been deposited from solution (such as a solution of the organic semiconductor dissolved in an organic solvent), good or optimum performance characteristics have been difficult to achieve.